As we know, a manually tightened drill chuck in the present art generally includes a drill body, jaws, a nut, a nut sleeve, a bearing, a front sleeve, and a rear sleeve. The three jaws are mounted respectively in three inclined holes that are trisection of said drill body. The nut is mounted in a nut slot of the drill body. The nut thread constitutes a thread drive mechanism together with the thread of the jaws. The nut sleeve is fixedly connected with the nut. Between the front sleeve and the nut or the nut sleeve a key type connection is adopted. The rear sleeve is fixedly connected with the drill body that is provided with a threaded hole or a tapered hole on its rear portion. During using after being mounted, the drill body is connected with a drive shaft screw of power machine by the threaded hole at its rear portion. The drive shaft drives the drill body and thereby brings the three jaws and the tool being clamped to rotate synchronously. While mounting and clamping the tool, the front sleeve and the rear sleeve are grasped by hands and are rotated from each other so that the nut connected with the front sleeve rotates relative to the jaws in the drill body. Through the thread drive between the nut and the jaws, the jaws are moved forwards along the inclined holes of the drill body to clamp the tool handle. While expecting to clamp the tool handle more firmly, one should exert strength to rotate the front and rear sleeve much by hands. As the twisting force from hands is limited, the clamping force acted on the tool handle generated from the drill chuck by manually rotating is at a lower level. Thus the clamped tool tends to get loosen when the working resistance is larger. The patent U.S. 005988653A disclosed a clamping device that clamps the tool handle in virtue of the power of the electric tool. However, the structure of the device is much complex.